[Pw_forum] Noncollinear magnetization and spin orbit coupling problem on Energy convergence and Spin
Xiao Shi
xiaos at Princeton.EDU
Sat Mar 1 20:30:31 CET 2014
Hi Mulwa and other PW users
Thanks for your advise. However, the same problem still happens.
Has anyone met this kind of situation before? I'm wondering if this is the problem of the system or I didn't set the correct parameters.
On Wed, 26 Feb 2014 2:56pm Winfred Mulwa <mulwawinfred at gmail.com> wrote
>Try to set conv_thr = 1.0 d -4 in the namelist electrons
>On Tue, Feb 25, 2014 at 11:41 PM, Xiao Shi <xiaos at princeton.edu> wrote:
>
>> Dear PW users
>>
>> I'm doing calculations on Bi2Se3 system and get some problem with the
>> magnetization of this system.
>> As Bi2Se3 is a topological insulator, I need large spin orbit coupling
>> effect which means I need to do noncollinear calculation.
>>
>> After adding O2 molecule on the surface, I did spin polarization
>> calculation where the energy doesn't converge and the system goes into
>> anti-ferromagnetic like shown below:
>>
>>
>> total energy = -5045.36386241 Ry
>> Harris-Foulkes estimate = -5045.36391863 Ry
>> estimated scf accuracy < 0.00001751 Ry
>>
>> total magnetization = -0.00 0.00 2.00 Bohr mag/cell
>> absolute magnetization = 3.42 Bohr mag/cell
>>
>>
>> If I continue for more steps, it will grows into very large
>> anti-ferromagnetic like 20 Bohr mag/cell for absolute magnetization which
>> is unphysical. The O2 I placed is far away from the surface and there
>> shouldn't be any spin polarization for pristine surface in reality. Also
>> the total energy doesn't change monotonically.
>>
>>
>> The input file is listed below:
>> This is a supercell system of Bi2Se3 with 2*2 in the hcp lattice and there
>> are 15 layers of atom for the slab with vacuum larger than 20ans (O2 is at
>> least 10ans away from the slab)
>>
>> &system
>> ibrav=4,
>> celldm(1)=15.992,
>> celldm(3)=6.555356882,
>> nat=62,
>> ntyp=3,
>> ecutwfc=30.0,
>> ecutrho=300.0,
>> occupations='smearing',
>> degauss=0.002,
>> noncolin=.true.,
>> lspinorb=.true.,
>> starting_magnetization(1)=-0.001,
>> starting_magnetization(2)=0.001,
>> starting_magnetization(3)=0.5,
>> london=.true.
>> starting_spin_angle=.true.
>> nosym=.true.
>> /
>> &electrons
>> mixing_beta=0.2
>>
>> ATOMIC_SPECIES
>> Bi 208.98 Bi.rel-pbe-dn-rrkjus.UPF
>> Se 78.96 Se.rel-pbe-n-rrkjus_psl.0.2.UPF
>> O 16.00 O.rel-pbe-n-rrkjus_psl.0.1.UPF
>> ATOMIC_POSITIONS {crystal}
>> O 0.582808125 0.518307602 0.030071968
>> O 0.438796581 0.511316952 0.033700923
>> Se 0.333363441 0.666726883 0.270506612
>> Se 0.333363312 0.166681597 0.270506668
>> Se 0.833409077 0.166681597 0.270506668
>> Se 0.833408961 0.666727129 0.270506668
>> Bi 4E-16 3E-16 0.298539365
>> Bi 8.34671E-08 0.500045262 0.298539398
>> Bi 0.500045295 -2.00018E-07 0.298539398
>> Bi 0.500045179 0.500045262 0.298539398
>> Se 0.666727117 0.333363441 0.332477455
>> Se 0.166681746 0.333363493 0.332477478
>> Se 0.166681629 0.833408578 0.332477478
>> Se 0.666726948 0.833408578 0.332477478
>> Bi 0.333363498 0.166681691 0.366247219
>> Bi 0.833408983 0.166681691 0.366247219
>> Bi 0.833408867 0.666726943 0.366247219
>> Bi 0.333363441 0.666726883 0.366247266
>> Se 3.44477E-08 0.500045237 0.394371017
>> Se 0.50004532 -1.51013E-07 0.394371017
>> Se 0.500045204 0.500045237 0.394371017
>> Se 5E-16 3E-16 0.394371148
>> Se 0.166681762 0.333363525 0.438001919
>> Se 0.166681646 0.833408563 0.438001919
>> Se 0.666726916 0.833408563 0.438001919
>> Se 0.666727117 0.333363441 0.438001924
>> Bi 0.333363644 0.166681764 0.466101291
>> Bi 0.83340891 0.166681764 0.466101291
>> Bi 0.833408794 0.666726797 0.466101291
>> Bi 0.333363441 0.666726883 0.466101294
>> Se 5E-16 4E-16 0.5
>> Se -1.1658E-07 0.500045162 0.5
>> Se 0.500045395 5E-16 0.5
>> Se 0.500045279 0.500045162 0.5
>> Bi 0.666727117 0.333363441 0.533898706
>> Bi 0.166681764 0.333363527 0.533898709
>> Bi 0.166681648 0.83340856 0.533898709
>> Bi 0.666726914 0.83340856 0.533898709
>> Se 0.333363441 0.666726883 0.561998076
>> Se 0.333363642 0.166681762 0.561998081
>> Se 0.833408912 0.166681762 0.561998081
>> Se 0.833408796 0.666726799 0.561998081
>> Se 7E-16 5E-16 0.605628852
>> Se -2.67539E-07 0.500045087 0.605628983
>> Se 0.50004547 1.51013E-07 0.605628983
>> Se 0.500045354 0.500045087 0.605628983
>> Bi 0.666727117 0.333363441 0.633752734
>> Bi 0.166681691 0.333363381 0.633752781
>> Bi 0.166681575 0.833408634 0.633752781
>> Bi 0.66672706 0.833408634 0.633752781
>> Se 0.33336361 0.166681746 0.667522522
>> Se 0.833408928 0.166681746 0.667522522
>> Se 0.833408812 0.666726831 0.667522522
>> Se 0.333363441 0.666726883 0.667522545
>> Bi -3.16627E-07 0.500045062 0.701460602
>> Bi 0.500045495 2.00018E-07 0.701460602
>> Bi 0.500045379 0.500045062 0.701460602
>> Bi 7E-16 6E-16 0.701460635
>> Se 0.166681597 0.333363195 0.729493332
>> Se 0.166681481 0.833408728 0.729493332
>> Se 0.666727246 0.833408728 0.729493332
>> Se 0.666727117 0.333363441 0.729493388
>> K_POINTS {automatic}
>> 3 3 1 0 0 0
>>
>>
>> I wonder has any meet this problem before and can give me some
>> suggestion on it?
>>
>> PS: I've tried increase degauss to 0.05Ryd and decrease mixing_beta to
>> 0.05 which doesn't help
>>
>> Best Regard
>>
>> Xiao Shi
>> Department of Chemistry
>> Princeton University
>>
>>
>>
>>
>>
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>>
>
>
>
>--
>Mulwa Winfred.
>D Phil Student, Computational Material Science Group,
>University of Eldoret,
>Eldoret, Kenya.
Best
Xiao Shi
Department of Chemistry
Princeton University
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